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November 13th, 2011, 10:53 PM  #1 
Newbie Joined: Nov 2011 Posts: 4 Thanks: 0  Find centroid of a curve ( y coord. ) under discrete valu
Hello, I have a set of discrete pairs ( x , y )  keys and values  2D discrete function's samples  a histogram of input digital image that I need to process. ( y = f(x) ) I need to find y coordinate of a centroid of a curve under a discrete 2D function ( histogram ) for special image processing after . I found next formulas for continues functions centroid: http://www.intmath.com/applications...troidarea.php I've tried to calculate y coord. of a centroid using average method for discrete function integration but I'm not sure about computation of y , how to identify x = f1(y) ( inverted ) and an intervals for computation in discrete case. How to do that : from having (x,y) discrete pairs set to find the y coordinate of centroid under the function y=f(x) curve for the given interval [a , b] ( size N )? I need pseudo code or C or Matlab code of calculation of the y: something like ( pseudocode ): function find_centroid ( map<Key,Value>input_hist ) returns int y; Can anybody post a link for such problem solved , such function implemented or description of the algorithm ? Thanks in advance , my web site: http://goo.gl/2gh7X 
November 14th, 2011, 01:23 AM  #2 
Newbie Joined: Nov 2011 Posts: 4 Thanks: 0  Re: Find centroid of a curve ( y coord. ) under discrete val
sorry there was an error to find centroid of an area not of a curve : Find centroid of an area ( y coord. ) under discrete valued 2D function Hello, I have a set of discrete pairs ( x , y )  keys and values  2D discrete function's samples  a histogram of input digital image that I need to process. ( y = f(x) ) I need to find y coordinate of a centroid of an area under a discrete 2D function ( histogram ) for special image processing after . I found next formulas for continues functions centroid: http://www.intmath.com/applications...troidarea.php I've tried to calculate y coord. of a centroid using average method for discrete function integration but I'm not sure about computation of y , how to identify x = f1(y) ( inverted ) and an intervals for computation in discrete case. How to do that : from having (x,y) discrete pairs set to find the y coordinate of centroid of an area under a discrete function y = f(x) curve for the given interval [a , b] ( size N )? I need pseudo code or C or Matlab code of calculation of the y: something like ( pseudocode ): function find_centroid ( map<Key,Value>input_hist ) returns int y; Can anybody post a link for such problem solved , such function implemented or description of the algorithm ? Thanks in advance , 

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